Positive crankcase ventilation (PCV) systems are provided in engines to reduce emission as well as to decrease the amount of oil leakage from the engine. PCV systems typically seal the crankcase and provide air flow therethrough via a pressure differential in the intake system such as in intake conduits upstream and downstream of a throttle. Therefore in some PCV systems, air is drawn into the crankcase via a port positioned upstream of the throttle and released from the crankcase in a port positioned downstream of the throttle.
European Patent (EP) 2182185 discloses a crankcase ventilation system in an engine providing circulation of air through a crankcase. However, the Inventors have recognized several drawbacks with the crankcase ventilation system disclosed in EP 2182185. For example, the crankcase ventilation system disclosed in EP 2182185 may malfunction, causing the pressure in the crankcase to rise. The malfunction may be brought about by freezing of the oil in the PCV lines caused by a drop in temperature. The PCV malfunction may also be caused by production tolerances and/or assembly variability of components in the PCV system, giving rise to increased crankcase pressure. The elevated pressure in the crankcase may lead to component degradation.
As such, in one approach, a PCV system is provided. The PCV system includes an oil return line coupled to a PCV oil separator and extending through a crankcase housing and a PCV bypass valve positioned in a wall of the oil return line, the PCV bypass valve opening when a pressure in the crankcase exceeds a threshold value and closing when a pressure in the crankcase falls below a threshold value. The PCV bypass valve decreases the likelihood of the crankcase as well as other sealed chambers in the PCV system from reaching undesirable pressures which may damage components in the engine and PCV system. Moreover, the integration of the PCV bypass valve into the wall of the oil return line increases the compactness of the PCV system and the engine, if desired. Therefore, it will be appreciated that the technical results achieved via the PCV system include increasing the system's compactness and decreasing the likelihood of component degradation.
Further in one example, the oil return line is coupled to an oil separator that is in fluidic communication with an intake conduit. The intake conduit may be upstream or downstream of a throttle. Therefore, when the PCV bypass valve is open gas flows through the oil return line through the oil separator and then to the intake conduit. In this way, crankcase gases release through the PCV bypass valve may be internally routed back to the intake system, further increasing the PCV system's compactness.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. Additionally, the above issues have been recognized by the inventor herein, and are not admitted to be known.